1. Field of the Invention
The present invention relates to a measurement apparatus that automatically tests the properties of a device under test on polar coordinates.
2. Discussion of the Background Art
A network analyzer is an example of a measurement apparatus having a polar coordinate display function (JP (Kokai) 64[1989]-88,165 (pages 2 and 3, FIG. 1)). Several types of polar coordinates are displayed by network analyzers. There are polar charts, as well as the Smith chart or immitance chart, which are modified polar charts. For example, the Smith chart is used to test the performance of electronic components. An example of testing the performance of electronic components is given below.
In general, testing the performance of electronic components is testing whether or not the measurements plotted on a Smith chart displayed on the screen of a network analyzer are within a circle having a pre-determined radius. The circle for this testing is called the test circle. For instance, electronic components pass the test when the measurement of the return loss thereof is approximately a certain complex impedance value. Today inspectors test the performance of an electronic component by affixing transparent film on which a circle having a pre-determined radius has been drawn on the screen of a network analyzer and confirming macroscopically whether or not the measurements of the electronic component are within that circle.
However, there are large fluctuations in the results of testing by macroscopic observation, and testing errors are readily produced. In particular, the test circle on the film is drawn with lines always of the same thickness and therefore, the measurement results can be hidden by the test circle, and so forth, and the testing error rate rises with points closer to the circle. There is also a problem in that it is difficult to identify a specific sweep point in the measurement results displayed with polar coordinates and therefore, it is difficult to use the test finding in combination with other tests. For instance, when filters are being mass produced and inspected, first the properties in the passband are tested using film on which the test circle has been drawn, and then overall band properties including the passband and the stopband are monitored with the sweep conditions being changed, but testing efficiency is poor. Furthermore, the measurement results of devices under test that require additional outside circuits are displayed away from the origin of the polar coordinates and therefore, when all measurement results are displayed together, the measurement results are observed in small size and this leads to testing errors. In addition, in this case it is difficult to watch the test results or measurement results while adjusting the device under test so that under optimum conditions, the measurement results are within the test circle.
The present invention provides a measurement apparatus with which it is possible to test a device under test on polar coordinates in order to solve the above-mentioned problems. Moreover, an object of the present invention is to provide a measurement apparatus with which it is possible to accurately test a device under test with stability without affecting the test circle. Additionally, the present invention provides a measurement apparatus having a test function that can be easily used in combination with other tests. The present invention also provides a measurement apparatus having a test function that facilitates the examination procedure. Furthermore, the present invention also provides a method and a program that make this apparatus feasible.
By means of the present invention, it is not necessary to draw a test circle on film, testing can be performed without displaying the test circle displayed on polar coordinates, measurement results can be displayed over the test circle when the measurement results are displayed on polar coordinates, and test circles of various shapes can be accurately set up. Moreover, the test range can be set. Therefore, measurements within a wide range that includes the test range can be simultaneously performed. Thus, the testing can be easily used in combination with other testing processes. Furthermore, as long as the difference needed for testing is calculated for all measurements, some of the operating functions of conventional network analyzing apparatuses can be salvaged and a testing function can be added with some modifications.